Carbonaceous pyropolymers possessing recurring units containing at least carbon and hydrogen atoms per se will find a wide variety of uses in the chemical and electrical field. For example, the composites in the form of powders may be used as electrocatalysts which are used in the preparation of an electrode for an electrochemical cell. Other composites which are in the form of shaped replications of particle aggregates in the form of rods, pellets, spheres, etc. may be used as supports for chemically active metals or as adsorbents which may be utilized in a fixed bed adsorption process. The shaped replications of particle aggregates which will have impregnated on the surface thereof a chemically active metal are useful in a wide variety of chemical reactions such as polymerization reactions, reforming reactions, hydrocracking reactions, as a catalyst support for ammonia synthesis, as a support for metal phthalocyanine complexes which will form a catalyst useful for sweetening of petroleum products such as gasoline, etc. The shaped replications will themselves possess the desired characteristics of surface area, pore volume, apparent bulk density, crushing strength, etc. which will enable their use as supports or in fixed bed adsorption processes without undergoing physical deterioration to form powders, dust, fines, etc. and thus limit the use of such a composite.
The carbonaceous pyropolymers possessing recurring units containing at least carbon and hydrogen atoms which are composited on an inorganic metal oxide support, may be prepared by any known method such as by contacting the inorganic support or substrate at an elevated temperature of from about 400.degree. to about 1200.degree. C. in a reducing atmosphere containing an organic pyropolymer precursor to form a carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms on the inorganic metal oxide support. The organic pyropolymer precursors which may be used would include members of the group consisting of aliphatic hydrocarbons, aliphatic halogen derivatives, aliphatic oxygen derivatives, aliphatic sulfur derivatives, aliphatic nitrogen derivatives, alicyclic compounds, aromatic compounds, and heterocyclic compounds. Of the aromatic hydrocarbons, the most common class which may be utilized to form this polymeric process includes alkanes, alkenes, alkadienes, alkynes, etc. Aliphatic oxygen derivatives may include alcohols, ethers, aldehydes, ketones, etc; aliphatic sulfur derivatives may include mercaptans, sulfides, etc; aromatic compounds may include benzene, naphthalene, etc. As can be seen, an extremely wide latitude can be exercised in the selection of the organic pyrolyzable compounds inasmuch as virtually any organic material that can be vaporized, decomposed and polymerized on the refractory oxide by heating will suffice. The resultant carbonaceous pyropolymer will possess recurring units containing at least carbon and hydrogen atoms; however, depending upon the pyropolymer precursor which has been selected, the pyropolymer may also contain other atoms such as nitrogen, oxygen, sulfur or, if a metal containing organic compounds has been employed, a metal such as tin.
In another embodiment, the composite may be prepared by impregnating the refractory inorganic oxide substrate with a solution of a carbohydrate material such as dextrose, sucrose, fructose, starch, etc. and thereafter drying the impregnated support. After drying, the impregnated substrate or support is then subjected to pyrolysis temperatures in the range hereinbefore set forth whereby a carbonaceous pyropolymer similar in nature to those hereinbefore described is formed on the surface of the refractory inorganic oxide support.
Heretofore, in order to obtain a carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms alone, the inorganic support was chemically leached from the carbonaceous pyropolymer. The leaching was effected by treating the composite with either an acid or a base, thereby forming a high surface area carbonaceous pyropolymer support in the form of a powder or a shaped replication of the original inorganic support. The leaching of the base material of the type hereinbefore set forth may be effected over a wide range of temperatures, said range being from about ambient (20.degree.-25.degree. C.) up to about 250.degree. C. or more for a period of time which may range from less than 1 up to about 72 hours or more. It is to be understood that the operating parameters of the leaching step will vary over a wide range and will be dependent upon a combination of time, temperature, strength of the leaching solution, etc. Examples of acids or bases which may be utilized to leach out the base material, that is, the inorganic support such as a refractory inorganic oxide, will include inorganic acids such as phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, etc. organic acids such as methyl sulfonic acid, ethyl sulfonic acid, propyl sulfonic acid, toluene sulfonic acid, etc., strong bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, etc. It is to be further understood that the aforementioned leaching materials are only representative of the class of compounds which may be used and that any chemical which is capable of removing the refractory inorganic oxide while retaining the high surface area of the carbonaceous pyropolymer may be used.
The methods of obtaining the carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms has been set forth in U.S. Pat. Nos. 4,090,978 and 4,329,260.
A disadvantage or drawback when employing this type of process for leaching out the refractory oxide substrate is that a large amount of waste material is formed by the leaching operation. Therefore, after dissolution of the refractory inorganic oxide substrate, further steps are required which include extensive filtering and washing of the remaining carbonaceous pyropolymer to remove the metal ions such as aluminum or silicon and the leaching material such as, for example, phosphoric acid from the carbonaceous pyropolymer. The resulting solutions are not easily regenerated or dissolved, the presence of these materials thus posing a problem which requires further equipment with an attendant added capitalization factor of the money required to prepare the desired material.
As will hereinafter be shown in greater detail, an alternate method for removing the substrate may be effected without requiring additional steps in the disposal of waste material.